A phase lock loop (PLL) is a control system that generates an output signal whose phase and/or frequency is related to the phase of an input signal. While there are several differing types, in some implementations, a PLL may be formed of an electronic circuit consisting of a frequency oscillator providing a periodic input signal or a reference signal, a controlled oscillator that generates an output signal and a comparator. To enable the comparator to perform a comparison, the output signal is typically fed back toward the reference signal, creating a feedback loop. The comparator thus compares the phase of the reference signal with the phase of the feedback signal and causes the controlled oscillator to be regulated to keep the phase of the reference and output signals synchronized or locked.
The reference and output signal frequencies may also be related. Consequently, in addition to synchronizing signal phases, a phase-locked loop may track a reference frequency, or generate a frequency that is related to, such as being a multiple of, the input frequency. These properties of a PLL allows it to be applied to variety of uses including computer clock synchronization, signal demodulation, frequency synthesis and frequency locking.
In some implementations, components of a PLL may be subject to microphonics, where the electrical behavior of the components may change in response to mechanical motion such as mechanical vibrations. For example frequencies generated by some oscillators and controlled oscillators may vary in response to mechanical vibration. The change in electrical behavior of components may thus degrade or impair the performance of a PLL. Accordingly, there is a need for a system and method for countering the effects of microphonics in a phase locked loop.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.